Merge pull request #34 from ridwanfathin/graph_fw

add flowd-warshall algorithm

graph/shortest_distance_fw.go

@@ -0,0 +1,57 @@
+// shortest distances between every pair of vertices using floyd-warshall algorithm
+// https://en.wikipedia.org/wiki/Floyd%E2%80%93Warshall_algorithm
+// http://www.golangprograms.com/golang-program-for-implementation-of-floyd-warshall-algorithm.html
+package graph
+
+import (
+	"fmt"
+	"math"
+)
+
+type graph struct {
+	to int
+	wt float64
+}
+
+func floydWarshall(g [][]graph) [][]float64 {
+	dist := make([][]float64, len(g))
+	for i := range dist {
+		di := make([]float64, len(g))
+		for j := range di {
+			di[j] = math.Inf(1)
+		}
+		di[i] = 0
+		dist[i] = di
+	}
+	for u, graphs := range g {
+		for _, v := range graphs {
+			dist[u][v.to] = v.wt
+		}
+	}
+	for k, dk := range dist {
+		for _, di := range dist {
+			for j, dij := range di {
+				if d := di[k] + dk[j]; dij > d {
+					di[j] = d
+				}
+			}
+		}
+	}
+	return dist
+}
+
+func main() {
+	gra := [][]graph{
+		1: {{2, 3}, {3, 8}, {5, -4}},
+		2: {{4, 1}, {5, 7}},
+		3: {{2, 4}},
+		4: {{1, 2}, {3, -5}},
+		5: {{4, 6}},
+	}
+
+	dist := floydWarshall(gra)
+	//dist[][] will be the output matrix that will have the shortest distances between every pair of vertices
+	for _, d := range dist {
+		fmt.Printf("%4g\n", d)
+	}
+}